Preparation method of cation exchange membrane with ion window

Abstract

The invention is suitable for the technical field of membrane materials, and provides a preparation method of a cation exchange membrane with an ion window, and the preparation method comprises the following steps: weighing biphenyl, isatin and tetraphenylporphyrin, and dissolving in dichloromethane; under an ice bath condition, dropwise adding trifluoroacetic acid at a constant speed, and then adding trifluoromethanesulfonic acid; and pouring the mixture generated by the reaction into deionized water to obtain a fibrous polymer solid, and washing the fibrous polymer solid with a sodium bicarbonate solution until the fibrous polymer solid is red. Dissolving the dried polymer in dimethyl sulfoxide, adding propane sultone, and eluting with acetone to obtain the functional polymer. And dissolving the functionalized polymer in dimethyl sulfoxide to form a red transparent solution, pouring the red transparent solution on a glass plate, and carrying out vacuum drying to finally obtain the cation exchange membrane. According to the cation exchange membrane disclosed by the invention, a supramolecular porphyrin structure is introduced, so that the ion exchange capacity and the chemical and mechanical stability of the membrane are remarkably improved, and a more efficient and reliable solution is provided for various industrial applications.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane materials, and in particular relates to a method for preparing a cation exchange membrane with an ion window. Background Art

[0002] Cation exchange membranes play a vital role in a variety of industrial applications such as water softening, demineralization, food processing and pharmaceutical manufacturing.

[0003] Traditional membrane materials of this type are usually made of linear polymers (such as polysulfone), which are widely used due to their excellent processing properties, but their insufficient durability in highly alkaline environments limits their application under harsh conditions.

[0004] Therefore, in view of the above situation, there is an urgent need to develop a method for preparing a cation exchange membrane with an ion window, improve alkali resistance and optimize ion transport properties, so as to overcome the shortcomings in current practical applications. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a cation exchange membrane with an ion window, aiming to solve the problems mentioned in the above background technology.

[0006] The present invention is achieved by a method for preparing a cation exchange membrane having an ion window, comprising the following steps: Step 1, weigh 3-5 parts of biphenyl, 4-6 parts of indigo carmine, and 0.01-0.2 parts of tetraphenylporphyrin, and dissolve these substances in 5-20 parts of dichloromethane; Step 2, under ice bath conditions, 1 to 3 parts of trifluoroacetic acid (TFA) are added dropwise at a constant rate, and then 10 to 33 parts of trifluoromethanesulfonic acid (TFSA) are added, and the reaction is continued for 3 to 5 hours; Step 3, pouring the green viscous mixture obtained by the reaction in step 2 into deionized water for elution to obtain a fibrous polymer solid; Step 4, eluting the polymer solid obtained in step 3 again with 1-3 mol / L sodium bicarbonate solution until it turns red; then placing it in a vacuum drying oven and drying it at 60-80° C. for 10-24 hours; Step 5, dissolving 1 to 3 parts of the dry polymer obtained in step 4 in 20 to 50 parts of dimethyl sulfoxide (DMSO), adding 1 to 3 parts of propane sultone, reacting at 60 to 80° C. for 5 to 8 hours, and eluting with acetone to obtain a functionalized polymer; Step 6, dissolving 0.5 to 1 part of the functionalized polymer obtained in step 5 in 10 to 15 parts of dimethyl sulfoxide (DMSO) to obtain a red transparent solution; Step 7, pouring the red transparent solution obtained in step 6 onto a glass plate, placing it in a vacuum drying oven, and drying it at 60-80° C. for 10-24 hours to finally obtain a cation exchange membrane with an ion window.

[0007] In a further technical solution, dimethylacetamide (DMAC) or dimethylformamide (DMF) is used to replace the dimethyl sulfoxide (DMSO) film casting solvent in steps 5 and 6.

[0008] According to a further technical solution, the thickness of the cation exchange membrane obtained in step 7 is 80 to 110 μm.

[0009] A further technical solution is that in step 1, 4.2 parts of biphenyl, 5.3 parts of isatin, and 0.2 parts of tetraphenylporphyrin are weighed and dissolved in 10 parts of dichloromethane.

[0010] According to a further technical solution, in step 2, 2 parts of trifluoroacetic acid (TFA) are added dropwise at a constant rate under ice bath conditions, and then 25 parts of trifluoromethanesulfonic acid (TFSA) are added, and the reaction is continued for 5 hours.

[0011] A further technical solution is that in step 4, the polymer solid obtained in step 3 is eluted again with 2 mol / L sodium bicarbonate solution until it turns red; then it is placed in a vacuum drying oven and dried at 80° C. for 24 hours.

[0012] According to a further technical solution, in step 5, 2 parts of the dry polymer obtained in step 4 are dissolved in 30 parts of dimethyl sulfoxide (DMSO), 2 parts of propane sultone are added, the mixture is reacted at 60° C. for 8 hours, and the functionalized polymer is obtained by eluting with acetone.

[0013] According to a further technical solution, in step 6, 1 part of the functionalized polymer obtained in step 5 is dissolved in 15 parts of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0014] According to a further technical solution, in step 7, the red transparent solution obtained in step 6 is poured onto a glass plate, and placed in a vacuum drying oven, and dried at 80° C. for 24 hours to finally obtain a cation exchange membrane with an ion window.

[0015] The present invention provides a method for preparing a cation exchange membrane with an ion window, which has the following beneficial effects: 1) Enhanced alkali resistance: By introducing the supramolecular porphyrin structure, the present invention greatly improves the alkali resistance of the cation exchange membrane. This improvement enables the membrane to be used in more harsh industrial environments, such as highly alkaline water treatment and electrolytic hydrogen production scenarios, thus overcoming the durability limitations of traditional polysulfone materials.

[0016] 2) Optimized ion transport properties: The unique cyclic organic structure of porphyrin increases the space inside the material, prevents excessively tight stacking between polymer chains, and provides a larger channel for ion migration. This design not only significantly improves the ion exchange capacity of the membrane, but also enhances its chemical and mechanical stability.

[0017] 3) Precisely controlled ion windows: By adjusting the content and distribution of supramolecular porphyrins, the present invention can achieve precise control of the size and functionality of the ion windows. These ion windows enhance the ion selectivity of the membrane and optimize the overall ion permeability, making it more suitable for specific separation processes. In addition, specific chemical modifications can further improve the screening efficiency of specific cations (such as calcium and magnesium ions in water softening, or potassium ions in food processing).

[0018] 4) pH response characteristics and visualization function: Tetraphenylporphyrin can not only be used as a branched structure, but also endow the supramolecular porphyrin ring with good pH response visualization characteristics. This means that the membrane will display different colors under different acid and base conditions, providing an intuitive way to monitor the state. This visualization function not only facilitates the evaluation and monitoring of membrane performance, but also provides instant operational feedback, enhancing safety and convenience during use.

[0019] In summary, the present invention has developed a new type of cation exchange membrane that performs well in chemical stability, ion selectivity and permeability by integrating supramolecular porphyrin structure and ion window technology. This membrane based on supramolecular technology is not only suitable for traditional water treatment and food processing fields, but can also be widely used in more demanding industrial environments, such as chemical raw material purification and the preparation process of pharmaceutical intermediates. Its flexible and adjustable ion window provides highly customized solutions for various industrial applications, greatly expanding the application range and efficiency of cation exchange membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the electrodialysis desalination process. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0023] Example 1 An embodiment of the present invention provides a method for preparing a cation exchange membrane having an ion window, comprising the following steps: Step 1, take 4.2 g of biphenyl, 5.3 g of indigo carmine, and 0.01 g of tetraphenylporphyrin, and dissolve these substances in 10 mL of dichloromethane.

[0024] Step 2: In an ice bath, 2 mL of trifluoroacetic acid (TFA) was added dropwise at a constant rate, followed by 25 mL of trifluoromethanesulfonic acid (TFSA), and the reaction was continued for 5 hours.

[0025] Step 3, pouring the green viscous mixture into deionized water for elution to obtain a fibrous polymer solid.

[0026] Step 4: In order to clean the acid inside, it is eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turns red. It is then placed in a vacuum drying oven and dried at 80°C for 24 hours.

[0027] Step 5, 2 g of the above-mentioned dry polymer was dissolved in 30 mL of dimethyl sulfoxide (DMSO), 2 mL of propane sultone was added, the mixture was reacted at 60° C. for 8 h, and the functionalized polymer was eluted with acetone.

[0028] Step 6: Dissolve 1 g of the above polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0029] Step 7: Pour the red transparent solution onto a glass plate, put it into a vacuum drying oven, and dry it at 80° C. for 24 hours. Finally, a cation exchange membrane AEM-1 with an ion window is obtained.

[0030] Example 2 An embodiment of the present invention provides a method for preparing a cation exchange membrane having an ion window, comprising the following steps: Step 1, take 4.2 g of biphenyl, 5.3 g of indigo carmine, and 0.1 g of tetraphenylporphyrin, and dissolve these substances in 10 mL of dichloromethane.

[0031] Step 2: In an ice bath, 2 mL of trifluoroacetic acid (TFA) was added dropwise at a constant rate, followed by 25 mL of trifluoromethanesulfonic acid (TFSA), and the reaction was continued for 5 hours.

[0032] Step 3, pouring the green viscous mixture into deionized water for elution to obtain a fibrous polymer solid.

[0033] Step 4: In order to clean the acid inside, it is eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turns red. It is then placed in a vacuum drying oven and dried at 80°C for 24 hours.

[0034] Step 5, 2 g of the above-mentioned dry polymer was dissolved in 30 mL of dimethyl sulfoxide (DMSO), 2 mL of propane sultone was added, the mixture was reacted at 60° C. for 8 h, and the functionalized polymer was eluted with acetone.

[0035] Step 6: Dissolve 1 g of the functionalized polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0036] Step 7, pour the red transparent solution onto a glass plate, put it into a vacuum drying oven, and dry it at 80° C. for 24 hours. Finally, a cation exchange membrane AEM-2 with an ion window is obtained.

[0037] Example 3 An embodiment of the present invention provides a method for preparing a cation exchange membrane having an ion window, comprising the following steps: Step 1, take 4.2 g of biphenyl, 5.3 g of indigo carmine, and 0.2 g of tetraphenylporphyrin, and dissolve these substances in 10 mL of dichloromethane.

[0038] Step 2: In an ice bath, 2 mL of trifluoroacetic acid (TFA) was added dropwise at a constant rate, followed by 25 mL of trifluoromethanesulfonic acid (TFSA), and the reaction was continued for 5 hours.

[0039] Step 3, pouring the green viscous mixture into deionized water for elution to obtain a fibrous polymer solid.

[0040] Step 4: In order to clean the acid inside, it is eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turns red. It is then placed in a vacuum drying oven and dried at 80°C for 24 hours.

[0041] Step 5, 2 g of the above-mentioned dry polymer was dissolved in 30 mL of dimethyl sulfoxide (DMSO), 2 mL of propane sultone was added, the mixture was reacted at 60° C. for 8 h, and the functionalized polymer was eluted with acetone.

[0042] Step 6: Dissolve 1 g of the above polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0043] Step 7, pour the red transparent solution onto a glass plate, put it into a vacuum drying oven, and dry it at 80° C. for 24 hours. Finally, a cation exchange membrane AEM-3 with an ion window is obtained.

[0044] Attached Figure 1This is a schematic diagram of the electrodialysis desalination process. The prepared membrane spacer is placed in the device. Under the action of the electric field, the anions and cations in the liquid will move in a directional manner, thereby achieving desalination and concentration. The performance of the prepared cation exchange membrane with ion windows is tested below: Test 1: The prepared membrane was tested for resistance and compared with commercial membranes Fuji No. Ⅰ cationic membrane and Nafion 115. See Table 1 for specific results.

[0045] Table 1 Surface resistance of the prepared membrane and two commercial membranes Test 2: The chemical stability of the prepared cation exchange membrane in sodium hydroxide solution was tested to investigate the chemical stability of the cation exchange membrane. The weight loss rate was used as an indicator and the weight difference was used as an indicator to evaluate its chemical stability. After being completely dried in a vacuum oven at 80°C for 24 hours, the weight of the sample was recorded. Then, the dried ion exchange membrane sample was soaked in a 2.0M sodium hydroxide solution at 80°C for 24 hours, 48 ​​hours, and 96 hours, and then the retained solution on the surface of the sample was carefully wiped, and the soaked membrane was washed with water until the water became neutral. Then, the ion exchange membrane sample was dried under vacuum conditions at 80°C for 24 hours, and then the membrane mass was re-weighed. The mass loss was used to characterize the alkali resistance stability. See Table 2 for specific results.

[0046] Table 2 Weight loss rate of membranes immersed in 2.0 mol / L sodium hydroxide solution at different time periods Test 3: Compare the water absorption of the prepared cation exchange membrane with Fuji No. Ⅰ cation membrane and Nafion115 at different temperatures. After the tested membrane sample is completely dried in a vacuum drying oven at 80℃ for 24h, the length of the membrane sample is recorded. Then, the dried ion exchange membrane sample is soaked in deionized water at 20℃, 30℃, and 40℃ for 48h. Then, the retained solution on the surface of the sample is carefully wiped and the weight of the membrane sample is recorded. Calculate the weight change of the sample compared to the dry state. See Table 3 for specific results.

[0047] Table 3 Water absorption of test film samples at different temperatures The above embodiment of the present invention provides a method for preparing a cation exchange membrane with an ion window, which is mainly reflected in the following aspects: 1) Enhanced alkali resistance: By introducing the supramolecular porphyrin structure, the present invention greatly improves the alkali resistance of the cation exchange membrane. This improvement enables the membrane to be used in more harsh industrial environments, such as highly alkaline water treatment and electrolytic hydrogen production scenarios, thus overcoming the durability limitations of traditional polysulfone materials.

[0048] 2) Optimized ion transport properties: The unique cyclic organic structure of porphyrin increases the space inside the material, prevents excessively tight stacking between polymer chains, and provides a larger channel for ion migration. This design not only significantly improves the ion exchange capacity of the membrane, but also enhances its chemical and mechanical stability.

[0049] 3) Precisely controlled ion windows: By adjusting the content and distribution of supramolecular porphyrins, the present invention can achieve precise control of the size and functionality of the ion windows. These ion windows enhance the ion selectivity of the membrane and optimize the overall ion permeability, making it more suitable for specific separation processes. In addition, specific chemical modifications can further improve the screening efficiency of specific cations (such as calcium and magnesium ions in water softening, or potassium ions in food processing).

[0050] 4) pH response characteristics and visualization function: Tetraphenylporphyrin can not only be used as a branched structure, but also endow the supramolecular porphyrin ring with good pH response visualization characteristics. This means that the membrane will display different colors under different acid and base conditions, providing an intuitive way to monitor the state. This visualization function not only facilitates the evaluation and monitoring of membrane performance, but also provides instant operational feedback, enhancing safety and convenience during use.

[0051] In summary, the present invention has developed a new type of cation exchange membrane that performs well in chemical stability, ion selectivity and permeability by integrating supramolecular porphyrin structure and ion window technology. This membrane based on supramolecular technology is not only suitable for traditional water treatment and food processing fields, but can also be widely used in more demanding industrial environments, such as chemical raw material purification and the preparation process of pharmaceutical intermediates. Its flexible and adjustable ion window provides highly customized solutions for various industrial applications, greatly expanding the application range and efficiency of cation exchange membranes.

[0052] Embodiments 1-3 are only preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the above technical content as inspiration to change or modify the equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments without departing from the technical essence of the claims of the present invention still fall within the scope of protection of the claims of the present invention.

[0053] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for preparing a cation exchange membrane having an ion window, characterized in that: The following steps are involved: Step 1, weigh 3-5 parts of biphenyl, 4-6 parts of indigo carmine, and 0.01-0.2 parts of tetraphenylporphyrin, and dissolve these substances in 5-20 parts of dichloromethane; Step 2, under ice bath conditions, 1 to 3 parts of trifluoroacetic acid are added dropwise at a constant rate, and then 10 to 33 parts of trifluoromethanesulfonic acid are added, and the reaction is continued for 3 to 5 hours; Step 3, pouring the green viscous mixture obtained by the reaction in step 2 into deionized water for elution to obtain a fibrous polymer solid; Step 4, eluting the polymer solid obtained in step 3 again with 1-3 mol / L sodium bicarbonate solution until it turns red; then placing it in a vacuum drying oven and drying it at 60-80° C. for 10-24 hours; Step 5, dissolving 1 to 3 parts of the dry polymer obtained in step 4 in 20 to 50 parts of dimethyl sulfoxide, adding 1 to 3 parts of propane sultone, reacting at 60 to 80° C. for 5 to 8 hours, and eluting with acetone to obtain a functionalized polymer; Step 6, dissolving 0.5 to 1 part of the functionalized polymer obtained in step 5 in 10 to 15 parts of dimethyl sulfoxide to obtain a red transparent solution; Step 7, pouring the red transparent solution obtained in step 6 onto a glass plate, placing it in a vacuum drying oven, and drying it at 60-80° C. for 10-24 hours to finally obtain a cation exchange membrane with an ion window.

2. The method for preparing a cation exchange membrane having an ion window according to claim 1, characterized in that: The dimethyl sulfoxide casting solvent in steps 5 and 6 was replaced by dimethylacetamide or dimethylformamide.

3. The method for preparing a cation exchange membrane having an ion window according to claim 1, characterized in that: The thickness of the cation exchange membrane obtained in step 7 is 80 to 110 μm.

4. The method for preparing a cation exchange membrane having an ion window according to any one of claims 1 to 3, characterized in that: In step 1, 4.2 parts of biphenyl, 5.3 parts of isatin, and 0.2 parts of tetraphenylporphyrin were weighed and dissolved in 10 parts of dichloromethane.

5. The method for preparing a cation exchange membrane having an ion window according to claim 4, characterized in that: In step 2, 2 parts of trifluoroacetic acid were added dropwise at a constant rate under ice bath conditions, and then 25 parts of trifluoromethanesulfonic acid were added, and the reaction was continued for 5 hours.

6. The method for preparing a cation exchange membrane having an ion window according to claim 5, characterized in that: In step 4, the polymer solid obtained in step 3 is eluted again with 2 mol / L sodium bicarbonate solution until it turns red; then it is placed in a vacuum drying oven and dried at 80° C. for 24 h.

7. The method for preparing a cation exchange membrane having an ion window according to claim 6, characterized in that: In step 5, 2 parts of the dry polymer obtained in step 4 are dissolved in 30 parts of dimethyl sulfoxide, 2 parts of propane sultone are added, the mixture is reacted at 60° C. for 8 hours, and the functionalized polymer is obtained by eluting with acetone.

8. The method for preparing a cation exchange membrane having an ion window according to claim 7, characterized in that: In step 6, 1 part of the functionalized polymer obtained in step 5 is dissolved in 15 parts of dimethyl sulfoxide to obtain a red transparent solution.

9. The method for preparing a cation exchange membrane having an ion window according to claim 8, characterized in that: In step 7, the red transparent solution obtained in step 6 is poured onto a glass plate, placed in a vacuum drying oven, and dried at 80° C. for 24 hours to finally obtain a cation exchange membrane with an ion window.

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